This application details the basic outline of a 36-month empirical investigation into the relationship between geriatric surgery and neuropsychiatric decline. The effects of 3 types of elective surgery, all performed under general anesthesia, will be studied: (1) TJR (=total joint replacement: (2) cholecystectomy and (3) inguinal hernia repair. The study Ss. will range in all from 55 years to those of 75 years and older. In addition to a pre-operative psychosocial history, a battery of 7 standardized measuring instruments will be administered, covering the cognitive, affective and functional-behavioral aspects of patient behavior. The measures to be utilized are. Mini-Mental State Examinations, Iowa Screening Battery of Mental Decline, Geriatric Depression Scale; Barthel Index, OARS IADL, Geriatric Life Events Scale, Illness Vulnerability Scale. In addition, the experimental SS will be monitored for post-operative delirious symptomatology by means of a delirium rating scale. The research design used is a multiple time series design, in which the dependent variable measures will be administered three times; once pre- operatively and at 4 weeks and 10 months post-operatively. A total of 225 experimental at 225 control Ss will be used. The design will be balanced in that the distribution of Ss over the experimental/control condition, types of surgery as well as age-groups will be equal. The control Ss will be matched with the experimental ones for sex, age, education and morbidity type. The design will test 5 major research hypotheses pertaining to the incidence of post-surgical decline in order patients, its moderation by sex, age and type of surgery and its relationship to post-operative delirium.